Ravenna. Museo Nazionale. Patera decorativa di Porta Aurea. – University of Bologna, Europe – CC BY-ND.
https://www.europeana.eu/en/item/22/_11589
https://commons.wikimedia.org/wiki/File:Frammenti_della_porta_aurea_di_ravenna,_43_dc,_01.jpg
Architectural fragments stored at National Museum of Ravenna, Hall of Porta Aurea [source]